Various methods and devices have been employed in shoes to add cushioning to the shoe and to provide complementary custom fitting configurations to the contours of a foot inserted into the shoe. For example, U.S. Pat. No. 5,313,717, which issued to one of the present inventors, is directed to a shoe which incorporates reactive-energy, fluid-filled cavities in the shoe mid-sole. As discussed therein, typical prior art devices provide cushioning and custom fit to the foot inside the shoe by constructing the shoe sole from a softer, more resilient material or incorporating fluid filled pads or bladders in the shoe.
The use of gels to provide a conforming fit or cushion is known in the prior art. However, the prior art gels generally set to fit the contours of a foot and do not provide a soft cushion fit or they are soft liquid gels that must be placed in a bladder.
Prior art gels, which have been used to provide comfort, conformity, and stability in shoe and sock liner applications, are heat sensitive, and tend to soften on heating. This softening can result in a loss of support and a decrease in stability.
In other shoes designed to provide cushioning or custom fitting, either an air filled foam or an air "pump" has been used to conform to the foot which is inserted into the shoe. The foam is a material that reacts to foot pressure by allowing the air therein to become compressed and/or escape and therefore resiliently compresses upon pressure from the foot. The material does not have the capability to expand to the non-pressure areas of the foot. Shoes that incorporate an air "pump" fill in air around the foot so that the shoe conforms to the foot therein, but in doing so, increases the pressure on the foot. This increased pressure and foot surrounding air pocket tends to greatly increase the foot temperature. Thus, these solutions provide fit or comfort either by merely displacing at locations of higher pressure or by increasing the pressure completely around the foot. Thus, these shoes do not conform fully to the foot therein at normal pressures.